What is the significance of $_SERVER["HTTP_REFERER"] in PHP?

$_SERVER["HTTP_REFERER"] is a server variable that contains the URL of the page that referred the user to the current page. It can be useful for tracking where users are coming from or for implementing security measures to ensure that requests are coming from expected sources. However, it is important to note that this variable can be manipulated or spoofed by the client, so it should not be relied upon for critical security checks. 

// Check if the HTTP_REFERER is set and matches a specific domain
if(isset($_SERVER["HTTP_REFERER"]) && strpos($_SERVER["HTTP_REFERER"], "example.com") !== false) {
    // Proceed with the desired action
    // For example, redirect the user to a specific page
    header("Location: https://www.example.com/thank-you.php");
    exit;
} else {
    // Handle the case where the HTTP_REFERER is not set or does not match the expected domain
    echo "Unauthorized access";
}

Keywords

$_SERVER HTTP_REFERER PHP web development HTTP headers

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